Regenerative hot-blast apparatus



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No. 248,483. Patented Oct. 18,1881.

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J. 0. LONG. REGENERATIVE HOT BLASTVAPPARATUS.

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J. 'G. LONG. I REGENERATIVE HOT BLAST APPARATUS. No. 248,483. PatentedOct. 18,1881.

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iTan STATES PATENT OFFICE.

JOHN 0. LONG, OF MEGHANIOSBURG, PENNSYLVANIA.

REGENERATIVE HOT-BLAST APPARATUS.

SPECIFICATION forming part of Letters Patent No. 248,483, dated October18, 1881.

Application filed April 27, 1881. (No model.)

. Apparatus for Metallurgical Furnaces, ot'which the following is aspecification.

My invention relates to certain improvements in regenerative hot-blastapparatus for metallurgical furnaces; and the improvements consist incertain combinations and arrangements of parts, which will be firstfully described, and then specifically pointed out in the claims.

Referring to the accompanying drawings, making part of thisspeoification,and in which like letters of reference indicatecorresponding parts, Figure 1 is a horizontal section through theperforated air cylinders and blocks on line. 2 c, Fig. 5. Fig. 2 is ahorizontal section through the gas and air connections on line y 3 Fig.5. Fig. 3 is a horizontal section through the air cylinders and blockson line z 2, Fig. (5, showing a modification of the dividing pipe,distributing main, connections, and combustion-chainber. Fig. 4 is ahorizontal section of the same on line y y, Fig. b. Fig. 5 is a verticallongitudinal section on line 00 00, Figs. 1 and 2, showing the hot andcold gas and hot and cold air and chimney connections. Fig. 6 is alongitudinal section on line mw, Figs. 3 and 4, showing the hot and coldgas and hot and cold air and chimney connections, the same being amodification of the parts shown in Fig.5. Fig.7 is a vertical sectionthrough the combustion-chamber on line a to, Figs. 1 and 2. Fig. 8 is avertical section through the combustion-chamber on line a a, Figs. 3 and4, showing a modification of the dividingpipes, connections, mains, andcombustion-chamber shown in Fig. 7. Fig. 9 is a vertical transversesection of the oven on line 'v Figs. 1,2,3, and 4. Figs. 10, 11, and 12are perspective views of portions of the walls, showing theirconstruction, so as to provide against the effects of expansion andcontraction. Fig.13 is a longitudinal vertical section on line 3/ 31 ofFig. 14 of an oven whose regenerator-tlues are arranged in groups orsets, showingthe modified method of forming the horizontaldistributing-fines. Fig. 14 is a horizontal section of the same on line:0 .20 of Fig. 13. Fig. 15 is a top or plan view of four combined ovensand gas-heaters arranged in couples directly connected, having twogas-supply mains at hot or combustion chamber sides. Fig. 16 is a top orplan view of four combined ovens and gas-heaters arranged in couples andhaving a common gas-supply main connected to their severalcombustion-chambers. Fig. 17 is a top or plan view of three combinedovens and gas-heaters arranged above a common gas-supply main. Fig. 18is a top or plan view of three ordinary regenerative hot-blast ovensaltered to my improved system Without adding a fourth ordinary oven or acombined oven and'gas-heater.

The object of this invention is to provide a regenerative hot-blast ovenwhich can be used either for heating the blast or for heating thecombustible gas burned in the apparatus, so thatitmay be substituted foreither a special blast-oven or a special gas-heater, or both, in orderto heat the combustible gas prior to its being burned in the apparatus,whereby a more intense heat may be developed therein than, when the.apparatus is heated by the combustion of gas which has not been heatedafter leaving its source, and which is so arranged with suitableconnections that it can be used either for heating the blastorforheating the combustible gas by being heated for each objectspecially; or itcan be used asa gasheater without being speciallyheated therefor by making available the large quantity of heat yet inthe oven when used to heat the blast after it has lost that portion ofits heat which is effective in'heating the blast to the requiredtemperature, and which combined blast-oven and gas-heater may besubstituted for either the special gas-heaters or blast-ovens, or forboth, as aforesaid, so that when used as agasheater it can, in case offailure or repair of the blast-ovens, be used for heating the blast,thus furnishing a duplicate set of blast-ovens without increasing thcost of the plant, and at the same time avoid g the danger incident to afailureof the hot blast by the giving out of the special blast-ovens;and in addition thereto the object is to furnish a means of altering theregenerative hot-blast apparatus now in use to my improved system,either by adding thereto one or more combined blast-ovens andgas-heaters directly connected thereto, so as to form couples, eachconsisting of anloven used as a gas-heater and an oven used as ablastoven, as hereinafter described, or all may be connected to a commonhot-gas main, as in Fig. 16, and in both cases adding to the other ovensthe necessary hot and cold gas and air connections, so that any or allmay be used as blast-ovens or gas-heaters, as desired; or a plantconsisting of four blast-ovens may be altered to my system where theovens are arranged along a common coldgas-supply main having no otherbranches by putting in the main a valve between the ovens andblast-turnace or other source of gas supply, and then using the portionthus cut ed as a hot-gas main or, in case each pair of ovens has acommon gas-supply main without other branches, then by cutting it oil asabove described a hot-gas main is formed leading from one oven to theother, and the pair is worked as a couple. In both cases the necessaryadditional hot and cold gasand air connections are made so that any ovenmay be used as a gas heater or blast-oven, as desired.

In the case of a plant consisting of three ovens it may, owing to thefact that the combustible gas necessary to heat the apparatus has am uchsmaller volume and less velocity and greater heatabsorbing power thanthe blast, while the specific heat is about the same in both cases, bealtered to my improved system without increasing the number of ovens, byaltering them into combined blast'ovens and gasheaters by adding to theovens the necessary cold-gas main and connect ions at the cool end, inorder to supply the gas to be heated, and at the hot end a hot-gas mainconnecting all of the ovens; or,in case the ovens have a commongas-supply main, then, by cutting it oft by a valve between the ovensand blastfurnace or other source of gas-supply, a hot-gas main isformed, using the ordinary gas-connections with the ovens for thepassage of the heated gas. with hot air, then the necessary connectionsmust be made as hereinafter described; but it cold air is used forcombustion, then the ordinary air-connections can be used.

A plant of three blast-ovens may also be altered by adding one of thecombined ovens and gas'heaters and the necessary blast and gas and airconnections to the other ovens and cutting off the gassupply main, asabove described.

The object is also to provide a means of heating a mixed blast of airand vapor, and at the same time furnish pure highly-heated atmosphericair for combustion in the ovens and gasheaters; also, to provid forexpansion and contraction and for the alual heating of the oven andequal distribution of the gas or blast to be heated.

In this specification when speakin gof cold or cool gas, I mean gas atthe temperature it has after leaving the blast-furnace or. other sourceof supply less the temperature lostin transmission to the apparatus inwhich it is burned-that is, combustible gas which has not been heatedafter leaving the apparatus in- If it is desired to burn the heated gaswhich it was produced and prior to its introductioninto the apparatus inwhich itis burned.

The tendency of modern blast-furnace engineering is to reduce thetemperature of the waste gases from the blast-furnace as low aspossible, and is a result of the widening of the blast-furnace throat,as now done in the more modern blast-furnaces, in order to save fuel andimprove the working of the furnace. In fact, one very high authoritysays the temperature ot' the waste gases ot a blastfurnace should notexceed 212 Fahrenheit; hence the necessity of having a means of heatingthe gas so as to be able to command an intenselyheated blast.

The invention consists in the regenerative hot-blast oven having coldblast or air and cold-gas and chimney connections at the cool or chimneyend, and having at the hot or combustionehamber end hot-blast andhot-gas delivery connections, as well as the hot and cold gas and hotand cold air connections for sup plying the necessary hot or cold gas toheat the oven by being burned therein by hot or cold air or bya mixtureof hot or cold air, and whose walls are so constructed as to provide forexpansion and contraction of the several walls, and whose root isconstructed as shown.

It also consists in the horizontal tines and the several connectingpipes and flues or distrilniting-mains at the cool end, whereby the gasor blast to be heated is equally distributed, and of the fines and pipesand mains at the hot end, whereby the combustible gas to be burnedtherein is equally distributed.

It also consists in the combustionchamber divided into single or doublecompartments by longitudinal walls extending from the root'and to ornear thebottom,andhavingtheair blocks or cylinders extending through thecasing and into the wall separating the comlmstion-chamber andregenerator.

It also consists in the combination of the pipes and valves by which hotair is supplied for combustion in the ovens or gas heatersindependent ofthe hot-blast main.

It further consists in the combination ofone or more of the abovedescribed ovens, used either as blast-ovens or gas-heaters, with one ormore ordinary regenerative or above-described ovens used as blast'ovens.

It further consists in the combination of two or more combined ovens andgas-heaters, which are used successively for heating the blast and forheating the combustible gas.

It further consists in the combination, with two or more ordinaryregenerative hot-blast ovens, of the necessary hound 001d gas mains, andconnections by which they may be used as blast-ovens andgas-heatem,oithar successively or in couples, allessentiml lymhereinafter more particularly described.

The combined oven and gas heater is constructed of ordinary fire-brickor of similarlyshaped blocks of fire-brick or other refractorymaterials, and whose dimensionavary with the temperature of the blastdesire-(1,150 that allof Ils crease s the material in the bricksorblocks may be useful in storing up and giving out heat, for withdifferent temperatures the depth to which the effective heat penetratesand is given off varies. Itisrectangularin form and is supported bycurved segmental walls A of common or red brick, sand, slag, &c., andincased in sheetiron; or it may be made without the supporting-walls A,with a rectangular casing of sheetiron properly supported by outsidegirders or bracing; or the sheets may be put on horizontally in stripswhose length is equal to the width of the several sides of the oven, andwith their edges upturned flange-like and fastened, thus providing forlateral pressure. It is divided into two partsB, the regenerator and O,the combustion-chamber-by the wall I), which extends from the bottom tonear the top, but allowing space for the horizontal tines S and fromside to side. Itis also divided into severalindependentcompartments,either double or single, by means of the roof-supporting walls E, whichextend from front to rear and from the roof to the bottom, except theregenerator part of those in the middle of the double compartments,which rest on arches tormiiig the horizontal flues G, and in thecombustion-chamber in which those forming the double compartmentsextend, either as in Fig. 7 to below the connection I,or, as in Fig.8,they extend to thetop of thehorizontal fine 0. They may extend, as inFig. 7, to the bottom, in which case each compartment would have apassage, as at I, for removing the dust.

The walls E in the middle of the double compartments may extend tobetween the airblocks or cylinders H, and the connection I for passageof blast and gas, as in Fig. 7, or they may be cut off above the aircylinders or blocks, as in Fig. 7; but in this case the air cylinders orblocks are supported by the walls J, to prevent sagging from the effectsof heat.

The combustion-chamber maybe constructed as in Fig.8, in which the wallsE in the middle of the compartments may be cut otf above the air blocksor cylinders. WVhen so modified the compartments may be made single byextending all of the walls E to the top of the flue O, and eachcompartment is provided with a connection, I. In order th at there maymore certainly be an equal distribution of the combustible gas and theheated products ot'combustion, the mouths of the connections I areplaced in the middle of each of the compartments, either double orsingle.

The air for combustion is introduced through the perforated blocks orcylinders H, placed either in the middle walls, E, of the compartments,as in Fig. 7, or in the walls which form the sides of the single ordouble compartments, as in Fig. 8. The air cylinders or blocks H extendthrough and even with the casing and into the wall D, so that in case ofrepair they may readily be replaced from the outside of the oven byremoving the connecting-pipe J and connections K.

The air blocks or cylinders may be made of fire clay or brick, metal, orother refractory material, and, if necessary. may be cooled by causingacurrent of air or water to tlow through a pipe, K, which may be embeddedtherein. The air cylinders or blocks H are connected by pipes J, havingregulating-valves M, to the pipe K, having valve L. The pipe K connectswith the pipe N, communicating with the combustion-chamber G and havingvalve 0, Figs. 1, 3, and 7, which may be made in the form of acheck-valve by having a suitable-sized seat-valve so balanced as to beautomatic, so as to prevent any back flow of air when the oven is beingheated or is heating gas; but when the oven is heating the blast opensautomatically to allow the air necessary for combustion in the otherovens to flow into the pipe N, and thence by the pipe A, which connectsit to the similar pipes, N, of the other ovens. When the ovens are inthe same line, as in Fig. 17, the pipe N extends only be yond pipe K, tomeet pipe A, which joins all pipes N; but when the ovens are oppositeeach other, as in Figs. 15 and 16, then the extension of the pipes N,after connecting by pipes A to meet the corresponding pipes N of theopposite ovens, is necessary to complete the circuit of the air-passagesfor the air for combustion independent of the hotblast main.

If in allof thecompartmentsexceptthatnext the cold-blast entrance ablast of steam or vapor be introduced in the connections F, togetherwith the cold air introduced by the cold-blast connection H,thenin allofthe compartments there will be a mixed blast, excepting the first, inwhich it will be of pure atmospheric air, and this will, by theconnection N, be fuinished for combustion,.while a mixed hot blast willbe supplied to the furnace. The pipe N is also connected to the cold-airmain 0 by the pipe Q having valve P, by which means cold air may besupplied for combustion.

The dust may be removed from the combustion-chamber through the openings1, which may also be used for tiring the gas. The dust in theregenerator is removed through the openings A The several compartmentsof the combustion-chamber are also provided with the connections I tothe distributingmain 0, connected to the dividingpipes P, which enterthe main 0 midway between the connections I, so as to equally distributethe combustible gas burned in the oven.

The main 0 may be formed like main G, outside of the oven, as in Figs.1, 2, and 5, when the connections I will be horizontal; or the main 0may be formed in the bottom of the combustion-chan'iber by arching itover, as in Figs. 3, 4, 8, and 14, and making the vertical connections Ito the several compartments.

The outside connections will be by the dividing-pipe P entering the ovenand main 0, thus formed midway between the connections I. The pipes Pare connected to the opposite oven by the pipe Q, having valve 0, eitherdirectly or by means of similar dividing pipes and distributing main, asillustrated in Figs. 1:: and 16. The pipeQ is connected to the hot blastmain B, Figs. 5 and 6, by means of the vertical pipe 1t, valve S, andbranches T. The opposite oven is connected similarly to thehot-blastmain B by the connection F.

In the case of a plant of four ovens connected directly with oppositeones, thus forming two couples, as in Fi s. 15 and 16, in each of whichone oven is used as a gas-heater, while the other is, used as ablast-oven, the pipeQconnectingeachcoupleisconnected with thecorresponding pipe Q of the other couple by the pipe P, in freecommunication therewith, having valves Q, by means of which hot gas maybe supplied from one oven used as a gas-heater to the other used as agas-heater by opening the valves to pass the proper quantity of gas. andthen leaving them open. The pipe Q is also connected to the source ofcold-gas supply by the valve \V and main W, by means of which cold gasmay be supplied to the ovens or gas-heaters for combustion.

The main may he used as a hot-gas main by placing a valve,\ ,in itbetween the ovens and the sonice ot' cold-gas supply, and may be commonto the opposite ovens or gas-heaters, as in Fig. 16, and conn cted toeach by connections having valves\\. This construction will admit ofthree ovens in a plant ot t'our ovens being used, or will give theadvantages of having gasheaters in a plant of three combined ovens andgas-heaters. In case of the three regenerative hot-blast ovens in theapparatus now generally used, they may he altered to my improved system,as in Fi 17, by adding the necessary llOt-tlll connections for supplyingthe air necessary for (.Ollll)LtSL-()ll it it is desired to burn-the gasby means of a blast of hot air, or the ordinary air-connections may beused, as in Fig. 18, by placing a valve, \W, in the cold-gas-supply main\V, thus cutting off communication with the furnace or other source ofcold gas supply and, forming a hot-gas main of the portion thus cut otf.The present gassnpply connection thus serves for the passage of theheated gas into and out of the oven, and then add a cold-gas mainflv andconnections L and valve 11 at the cool ends in order to supply the gasto be heated in the apparatus, as in Fig. 18.

The above construction of the main W will allow ot' the apparatus beingextended, as in case of four ovens and gas-heaters, with a minimum cost,by additional ovens to the common main.

The regenerator B is composed of the walls E and I), t'orn'iin'g thevertical tlues T. The walls I) extend from the horizontal flues G ashigh as the wall D, so as to allow sufficient space for the horizontaltlue S. The fines T are arrangid in one set, as in Figs. 5 and 6,

so that the products of combustion and gas or blast to be heatedpassthrough theregenerator in but one direction-that is, the former passdown while the latter pass upthus decreasing the friction. Theroof-supporting walls E extend from thelbottom to the roof, except inthe double compartments, in which they commence at the top of the archessupporting them.

The flues G are either single or double. In the latter case they areformed by the arches carrying the walls D and middle walls, E, of thedouble compartments. In either case they have the connections F placedin the middle of the compartments for the passage of the blast or gas tobe heated, as well as the products of combustion. The connections Fconnect with thedistributing-mainG,havingcoldblast connection and valveH, and chimneyconnections M, and communicating with the cold-gas-supplymain 7 by the dividing-pipes L, having valve R. The pipes L are soplaced as to be midway between the connections F, which open into themiddleot'thecompartments, so as to equally distribute the gas to beheated. The distributing-main G and connections F also serve. to equallydistribute the blast to be heated. It" the tluesare arranged as in Fig.13 then the distributing-main G may be formed in the lower part of thelast set of flues by arching it over and making themain G thus formedcontinuous, asin the combustion-chamber, Fig. 8, by removing parts ofthe walls E and making vertical openings corresponding: to theconnections F and opening into the middle of the compartments. Theconnection of the coldgas main will then he by the dividing pipes L,having valve R and entering the oven and main G thus formed midwaybetween the openings F, which may be made into each compartmentseparately or may open into two jointly. The chimney and cold-blastcommunications may then be made directly to the oven and opening intothe main G thus formed, as shown in Fig. 14. The vapor-pipe J, havingvalve 10, has branches L" extending into all of the connections F,excepting the one next the cold blast connection, Figs. 1, 2, and 5, andinto which they discharge the steam or vapor. In case of forming main Gin oven, as in Figs. 13 and 14, then the branches L open into thecompartments above the main G if it is desired to heat a mixed blast.

The roof is formed of a number of rectangular blocks N and wedge-shapedblocks R of fire-brick or other refractory material, and whose lengthequals the distance between the centers of the roof-supporting walls E,upon which they rest. The wedge-shaped blocks are placed in those partswhich are removed when access is desired, as shown in Figs. 5 and 6.

The root" blocks are covered with strips of sheet-iron E, whose widthequals the length of the blocks, and having upturned flange -like edges0 which are bolted together and held in place by the girders 1P, placedtransversely upon the flanges and fastened to the outside casing, asshown in Figs. 7,8, and 9. The strips E extend only over each portion,either that over the wedge-shaped blocks, and which is removed whenaccess is desired, as in clean- IIO ing, or over that formed by therectangular blocks. The strips E covering the wedgeshaped blocks mayslightly overlap the strips E" covering the rectangular blocks, and towhich they are bolted, and may, if necessary, be held down by girders;or the strips E covering the wedge-shaped blocks may meet the strips Eover the rectangular blocks with upturned flange-edges 0 as in Figs. 5and 6, and bolted together. In case access is desired for cleaningthegirders, if used, the sheetiron strips E and wedge-shaped blocks underthem only need be removed.

The several walls of the oven and gas heater are constructed of ordinaryfire-brick or similar rectangular-shaped blocks of fire-brick or otherrefractory materials, whose dimensions vary with the temperature of theblast desired and the temperature to which they are exposed, so that incase of the hotter blast they may be made larger as the depth to whichthe effective heat is absorbed and subsequently given out increases withthe temperature. The bricksor blocks are laid diagonally in reversedirections in the adjacent walls or courses in the same horizontalplanes and in the adjacent courses in the same vertical planes, as shownin Figs. 10, 11, and 12, and they are laid on edge or flat, as abovedescribed. The walls may also be made by having the bricks or blocksplaced on end and overlapping diagonally to different distances.

The bond is formed by having a horizontal bonding-brick, 13-, extendingfrom one wall to the other, and which is itself held in place and bondedby the vertical bonding-bricks D placed at each side and alternate endsof the ho izontal bonding-bricks B The bondingbricks D extend from themiddle of one horizontal bonding-brick, B across the next and to themiddle of the third, and, in addition, the boiuling-bricks D breakjoints, as in Fig. 10. The bonding-bricks D may also be placedhorizontally, as shown in Fig. 11. The walls may also be bondedhorizontally by a bond-brick, E extending from the middle of one wall tothe middle of the bond-brick B as in Fig. 10.

The walls maybe made bylaying the bricks flat and diagonally and inreverse directions,

as shown in Fig. 12, and bonded by a single bond-brick, F and by a partof a brick, l and a whole brick, G extending into the side wall, asshown. The next bond formed in this manner-by a whole brick, G and partI is so arranged that the whole brick Gr shall extend into the otherwall, as shown in Fig. 12. This construction of the walls E and D iscontinued until they reach the top of the fines T, when the walls E areconstructed by laying the bricks diagonally and in reverse courses, asthe wallsD were constructed, as shown in Fig. 11, until they reach theirproper height.

By having the bricks laid diagonally and in reverse courses and bondedin manner shown, the effects of expansion and contraction areefiectually provided against, which is a matter of the greatestimportance in regenerative hotbla'st ovens. In some cases this'isprovided for by saving a space between the brick-work of the oven andthe casing; in others by having walls with loose sliding bricks bothbetween the walls and the casing. In all these cases the expansionsought to be provided for is due to the summation of the expansions ofall the abutting bricks in the several walls as ordinarily constructed,and which resultantis transferred to thecasing to there be met; whereasin my arrangement each brick is free to expand harmlessly into-the fluesand not to add its linear expansion to that of the others in the samecourse, as when they abut as in ordinary wall, and so transfer the wholeexpansion to the outside casing. The lateral expansion of the bricks isharmless and only has a tendency to turn the bricks to a greater anglewith the wall. Those forming the bond, as B expand by pressingdiagonally the ones against which they abut, or if the walls are laid asshown in lower part of Fig. 11, in which two bordingbricks, B are used,then the expansion is perfeetl y free. By constructing the walls thusthe expansion is provided for as it is produced in each separate brick,while in the old or ordinary method of constructing the walls, in whichthe bricks abut, the resultant of all the expansions is transferred tothe outside casing, which must be very heavy in order to counteract it.In addition to providing for expansion and contraction, the strength ofthe walls is very greatly increased, so that they can be made muchthinner without fear of buckling, and at the same time the efficiency ofthe material is greatly increased, owing to the fact that the brickscomposing the walls extend through the walls from flue to flue and arenot shut off by a coating of mortar, which in practice is found to be amuch poorer conductor of heat than the fire-brick. Even a thin coatinglike a wash prevents to a marked degree the passage of heat.

A wall constructed as shown has a greater power of conducting heat intoor out of the wall than when the wall is made of several courses ofbrick each parallel to the direction of the wall, for in the case of afourteen-inch wall those bricks that are surrounded by mortar arepractically of but little, if any, benefit either in storing up orgiving out heat. This defectis avoided by theconstruction as shown inFigs. 10, 11, and 12.

The various valves used in the apparatus may be of any suitableconstruction.

Methods of working: When using the oombined blast-oven and gasheater asa gas-heater, supposingallvalvesclosed,proeeed as followsin order toheat it: Open the chimney-valve M"; then admit air for combustion byopening the valve L and the regulating-valves M, which remain open afterhaving been properly set; then open valve W to admit cold gas, when themain W is used as a cold-gas main, or hot gas when the main W is used asa hot gas main by closing the valve TV when the apparatus is arranged incouples, as before described; then IIC the hot combustible gas maybeadmitted to one gas-heater from the other through the pipe P by openingthe valves Q to the proper extent and leaving them open. Now, after theapparatus has become sufficiently heated, in order to heat thecombustible gas proceed as follows: Close the air-supply valve L; thenclose the gas'supply valve it cold combustible gas is admitted, but ifthe main is used as a hot-gas main then valve W remains open or isopened more fully to allow the heated gas to passinto the mainWused as ahot-gas main; then close the chimney-valve M and open thecold-gas'supply valve It to admit cold gas from themain W then, if thehot gas passes directly to the opposite blast-oven, open the bot-gasvalve G. The valves Q remain open so as to pass the hot gas from oneeven used as a gas-heater to the other used for the same purpose, thusfurnishing a supply of highlyheated combustible gas. Then, after thegasheater has parted with its eii'ective heat it is reversed and againheated when used in couples as follows: Close the hot-gas valve and thecold-gas valve R and open the chimney-valve M and air-supply valve L.The hot gas to be burned is admitted through the valves Q,which remainopen. If cold gas is burned then it is admitted from the main W by thevalve 7'. I11 case the main is used as allot-gas main, then the valve \Vremains open or is only partially closed.

When the combined oven and gas-heater is used as a blast-oven, in orderto heat the oven, all valves being closed, proceed as follows: Open thechimnevvalve M; then open the hotgas valve G, if the gas is suppliedthat way, or if the gas is supplied by the main \V, used either as a hotor cold gas-main, then open the valve 1V instead of C then open theair-valve L and the regulating-valves M, which, when properly set,remain open, by which means the oven becomes highly heated by burningtherein a highly-heated or cold gas with a blast of highly-heated air.After the apparatus has become sufficiently heated it is reversed and ahighly-heated blast produced, as follows: Close the gas-supply valve 0or \V, as the case may be; then close the chimney-valve M and open thecold-air-hlast valve H, and the steam or vapor valve K if a mixed blastis heated; then open the hot-blast valve S, by which means a blast ofhighly-heated air or a mixed blast of air and vapor is supplied. Thevalve L always remains open when the apparatus is used as a blast-oven.Then, after it has parted with its effective heat it is reversed andagain heated by closing the hot blast valve S, then closing the cold-airvalve H, and the valve K if used, and opening the chimney-valve M. Itmay be necessary, owing to the pressure on the valve M, to open asupplementary valve or a dust-door, opening outwardly to relieve thepressure by allowing the air to escape, or a slide-valve may besubstituted for the seat-valve. Then open the gassupply valve (1 or W,as the case may be.

When one or more above-described combined ovens and gas-heaters are usedin c0m bination and directly connected with one or more blast-ovens,thus forming couples, each consisting of a gas-heater and blast-oven, inthe reversal ofthe couples the blast-ovens must be reversed first in thefollowing manner: Supposing that in one couple, A and 13*, Figs. 15 and16, the gas-heater A is, as above described, heating the combustible gaswhich is burned in its blast-oven B as above described, and that in theother couple, 0 and D Figs. 15 and 16, the gas-heater C is being heatedwhile its blast-oven I) is heating the blast, as above described, then,after the blast-oven D and gas-heater A or either of them, has partedwith its effective heat, or the other oven B and gas-heater C or eitherof them, has be.- come sufficiently heated, the reversal is as follows:Always comniencingwith the blast-oven B which is being heated, in whichclose hotgas valve and the chimney-valve M and open the cold-blast valveH and the hot-blast valve S, so that there may always be a hotblastgoing to thefurnace and a pressure maintained in the pipes N, pipes A,and pipes K and connections, then reverse the gas-heater (J in the othercouple, which has been heated, by closing the air-valve L and thechimneyvalve M and open the cold-gas valve B, so that there may alwaysbe a suflicient supply of heated gas; then reverse the other blastoven Dwhich has been heating the blast, by closing the hot-blast valve S andthe cold-blast valve H, and opening the chimney-valve M andhot-gassupply valve G and the air-supply valve L, which then remainsopen while the oven is used as a blast-oven then reverse the othergas-heater A by closing the coldgas valve R and opening thechimney-valve M and the air-valve L, gas for combustion being admittedby valve W or Q, as the case may be, as above described. Then, after asuitable interval, the apparatus is ItWGI'St'd in the same way.

In thecase of altering, asin Fig. 18, a plantof the three regenerativehot-blast ovens generally used to my improved system without adding afourth oven or gas-heater, and working them or three of theabove-described combined blastoveus and gas-heaters, asin Fig. 16,inboth cases as blast-ovens and gas-heaters successively, and in both ofwhich cases theheated gas is conveyed from the oven in which it isheated to the oven in which it is burned by means of a common hot-gasmain or aportion of the usual cold-gas main, W, cut off for the purposeof being used as a hot-gas main by means of the valve W, as beforedescribed, so that at any time cold gas may be used in the usual way,the heated gas is burned by a blast of heated air, as in Fig. .17, or byordinary methods in other ovens, as in Fig. 18.

This method of working with three ovensis somewhat different from theabove-described methods, and is based on the fact that the oven whichhas heated the blast still contains a large amount of heat which is notof a sufficiently-high temperatureorintensity toheatthe blast to thedesired degree,butwhich can heat the combustible gas. sufficiently high,owing to the gas having a much less volume and velocity and greaterheat-absorbing power than the blast, and is as follows: Supposing allvalves closed; then, in the first oven, 11, open the cold-blast valve H;then the hot-blast valve S; then in the second oven, 1 open thecoldgas-supply valve R at chimney side of the oven; then open thegas-valve \N at the combustion-chamber; then in the third oven, K openthe chimney-valve M" and the gas-valve W at the combustion-chamber toadmit the gas to be burned; then open the air-valve L, Fig. 17, or theordinary air-valve L, Fig. 18, to supply air for combustion, by whichmeans this oven K becomes heated; then after a suitable interval theapparatus is reversed as follows: Always commencing with the oven K,which is being heated, in which close the gassupply valve W at thecombustionchainber, and the air-valves L supplying air for combustion,then close the chimney-valve M and open the cold-air-blast valve H, andthen the hot-blast valve S; then in the other oven, H through which theblast is passing, close the hot-blast valve S and the cold-blast valveH, and open the chimney-valve M, to allow the air in the oven H to passout through the chimney; then open the gas-valve W at thecombustion-chamber, and after a suitable interval, so as to allow theair in the oven to be drawn into the chimney and the oven to be filledwith gas, in order to avoid the danger of an explosion from a mixture ofair and gas in the oven and hotgas main, then close the chimney-valve Mand open the cold-gas valve R at the chimney side of the oven, thushaving gas pass through the oven and into the hot-gas main;thenintheother oven,I through which gas is passing, close the cold-gasvalve R at chimney side of the oven and open the chimney-valve M and thevalves L, to supply the air necessary for combustion, by which meansthis oven 1 becomes heated. Then, after the oven K which isheating theblast, has part ed with its effective heat, or the one, 1 which is beingheated, has become sufficiently heated, the apparatus is reversed in thesame manner, always commencing with the oven 1 which is being heated,and then the oven K, which is heating the blast, and lastly reverse theoven H which is heating the gas. Now, after the first reversal,theapparatus is heated with cold gas burned with hot or cold air,dependingon the system used while a heated blast'is being furnished.After the second reversal the apparatus is heated by the hot gas burnedwith hot or cold air, depending on the system used, in addition tofurnishing a highly-heated blast to the furnace, and so on. After eachreversal hotter gasis used with hotter air, and thus after each reversala hotter temgerature is developed.

In changing the oven which is heating the blast so as toheatthe gas, itmay be necessaryto open a supplementary valve or dust-dooropeningoutward to take the prcssurcotl'oi'thechimney-valve if it is ascat-valve, or a slide-valve may be substituted. It may be found inpractice that the opening of the chimney-valve in the reversal of theoven which has been heatingthe blast is unnecessary. Then the reversalcan be made by closing the hot-blast valve and cold-blast valve, openingthe gas-valve at the combustion -chamber, and then the coldgas valve atthe chimney side of the oven.

The following method of working may be used instead of those beforedescribed: Supposing one oven, H is heating the blast, the other, 1*",is being heated, while the third, K is heating the gas; then, in orderto reverse the apparatus, always commence with the oven 1 which is beingheated, in order to always have blast going to the furnace, and reverseit as follows: Close the gas-supply valve W connecting with the hot-gasmain W, and close the valves supplying the air for combustion and thechimney-valve M; then open the cold-blast valve H and the hot-blastvalve S, thus causing a current of air to flow through it and furnishinga highly-heated blast; then in the other oven, H through which airispassing, close the hot-blast valve S, and then the cold-blast valveH,and open the chimney-val ve M, to allow the air in the oven to passout through the chimney; then open the gas-valve W at thecombustion-chamber, and after a suitable interval, so as to allow theair in the oven to be drawn into the chimney and the oven to be filledwith gas, in order to avoid the danger of an explosion from the mixtureof air and gas in the oven and hot-gas main, then close thechimney-valve M and open the coldgas valve R at the chimney side of theoven, thus having gas pass through the oven and become highly heated andpassed into the hot-gas main; then in the other oven, K on gas close thecold-gas supply valve It at the chimney side of the oven and open thechimney-valve M, and then open the valves supplying the air necessaryfor combustion, by which means this oven K becomes highly heated. Then,after the oven 1 which is heating the blast, has parted with itseffective heat, or the one,'K which is being heated, has becomesufficiently heated, theapparatus is reversed in the same manner, alwayscommencing with the oven K which is being heated, then the one, 1 whichis heatingthe blast, and lastly reversethe one, H heating thecombustible gas, thus producinga more intensely heated blast after eachreversal.

In changing the oven which is on blast to heating gas the sameprecautions should be taken as in the other methods.

In the case of arranging four or more com bined blast-ovens andgas-heaters or four or more ordinary regenerative hot-blast ovenschanged into combined blast-ovens and gas-

